Envelope construction for vacuumized electric switch including means internally providing capacitive voltage division between adjacent terminals



J. E. JENNINGS Aprll 13, 1965 3,178,541

ENVELOPE CONSTRUCTION FOR VACUUMIZED ELEcTRIc SWITCH INCLUDING MEANS INTERNALLY PROVIDING CAPACITIVE VOLTAGE DIVISION BETWEEN ADJACENT TERMINALS Filed Feb. 16, 1961 J0 EMMETTJEN/W/VGS By GiWW 121's A770 EY United States Patent ENVELOPE CONSTRUCTION FOR VACUUMIZED ELECTRIC SWITCH INCLUDING MEANS IN- TERNALLY PROVIDING CAPACITIVE VOLT- AGE DIVISION BETWEEN ADJACENT TERMI- NALS Jo Emmett Jennings, San Jose, Calif., assignor, by mesne assignments, to Jennings Radio Manufacturing Corporation, San Jose, Calif., a corporation of Delaware Filed Feb. 16, 1961, Ser. No. 89,696 7 Claims. (Cl. 200144) My invention relates to vacuumized electric switches and particularly to such switches in which the interior ,walls of the vacuumized shell are provided with shielding means to prevent harmful deposit and accumulation of tungsten vaporized from the switch contacts.

Among the several objects of my invention are:

The provision of means for shielding the interior wall of the shell against a continuous deposit of tungsten, and thus preventing a destructive flash-over.

The provision of a vacuum switch in which external radiant heat can be used to degas the envelope as well as the shielding means within it.

The provision of a vacuum switch in Which the principle ,of capacity voltage division is applied to maintain a high over-all end-to-end stand-off voltage.

v The provision of improved switch contacts in which large areas are brought together or separated, so that heavy currents can be handled with a minimum of sparking and consequent volatilizing of the contact metal.

The provision of a vacuum switch assembled in two sections which may be cut apart to permit access to the interior for repair and reassembly.

The provision of an extremely rugged, high power, high voltage switch and one without need of sputter shields.

Other objects of the invention together with the foregoing will be set forth in the following description of pre ferred embodiments of my invention which are illustrated in the accompanying drawing. It is to be understood that I do not limit myself to the showing made by. the said descriptions and drawings, as I may adopt variations of my preferred forms Within the scope of my invention as set forth in the claims.

- on an enlarged scale, showing the annular rings seen in the upper part of FIG. 1.

FIGS. 4 and are fragmentary views in vertical section and on an enlarged scale, each showing an arrangement of shielding rings or skirts.

In the production of a rugged, high voltage, high power switch, a number of serious problems confront the designer. Among them are heating and vaporizing of the contact metals resulting in a shortened useful life of the switch. Especially troublesome is the fouling of the in side surface of the switch envelope with a conductive deposit of vaporized tungsten.

In my attack on these difiiculties I have also secured other benefits and advantages, including a double break switch having a low impedance path between the two contacts, with the advantage of large contact areas and which can be operated at twice the potential normally achieved with the single break switch.

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My switch design lends itself to low inductance, high power applications where the outer conductor may be securely mounted in a large plate.

In detail and referring first to FIG. 1, my switch comprises a vacuumized and hermetically tight envelope of generally cylindrical shape. The body of the envelope is formed of two cylindrical ceramic shells 2 and 3 having grooves formed on the inside surfaces. The shell may consist of a single piece and the grooves 4 cut or molded in the inside surface; or the shell may be a unitary structure built up of assembled rings 6, metalized on their edges and brazed together, the grooves 7 being formed on an inner edge, out or molded prior to assembly and brazing. Where the shell consists of a plurality of assembled rings 6, as shown best in FIG. 3, one ring of each pair of adjacent rings is provided with a rabbet 7 formed in its exterior surface at its united edge, and the other ring of the pair is formed with an annular flange 7" complementary to the rabbet. This construction facilitates assembly of the ring because it provides a means by which the separate rings are automatically axially aligned.

My switch envelope body may be formed of differently grooved shells or only of one type, but for illustration in FIG. 1, I have shown two types 2 and 3, hermetically joined by means of metallized edges to a metal or conductive feed-out ring 8 having one or more lugs 9 for circuit connections.

The upper end of the cylindrical body of my switch is closed hermetically by a metal plate 11 attached to the edge of the body by two union rings 12 and 13 integrally united at their outer edges 14. Ring 12 is brazed to the edge of the closure plate 11; and ring 13 is brazed to the top nietallized surface of the shell 2. Similar unions 16 and 17 hermetically join the two shells to the central feed-out ring 8 and to the closure plate 18 at the lower end of the envelope. The purpose of these unions is to provide a convenient andsecure means of connection between the parts, and also to provide access for service and repair to the interior of the envelope, it being remembered that especially in the larger sizes, my switch is inherently a costly product. By burning with a torch or otherwise cutting the edge 14 of the union, the shell may be opened as necessary for inspection and repair, then the edges of the rings rebrazed and the envelope again processed through the tubulation 19.

concentrically brazed on the inside of the closure plate 11 is a massive copper contact stud 21 capped at its lower or contact end with a disk of tungsten 22. A heavy screw 23 threaded through the closure plate and into the stud secures the connector plate 24 on top of the switch envelope.

Supported by brackets 26, integral with feed-out ring 8 on its inner edge and adjacent the inside surface of the shell 2 is a tungsten contact ring 27, the lower face of which is in planar alignment with the lower face of the tungsten disk 22. The contact ring concentrically surrounds the disk 22 to define therewith an annular passageway between the interiors of the shells 2 and 3 which is open when the switch is open but is blocked when the switch is closed.

Means are provided for shorting between the contact stud 21 and the contact ring 27 with a wide area of engaging surfaces so that heavy currents can be handled through my switch with a minimum of sparking, heating and volatilizing of tungsten contact surfaces. This is accomplished by mounting an annular shorting plate 28 of tungsten on a steel backing plate 29 and the two on a central axially movable stern extending out of the envelope, and operated as desired to open and close the switch contacts by an external operator means. It should be noted that when the shorting plate 28 engages both the stud 21 and contact ring 27, the annular space therebetween is blocked, thus effectively isolating the interior of the upper shell 2 from the interior of the lower shell 3.

integrally united to the lower closure plate 18 and depending therefrom is a cylindrical housing 31, closed at the lower end by plate 32, integral with a vertical inwardly extending bearing 33. Slidably disposed in this hearing is the shaft 34, the external end of the switch operating stem, which extends into the envelope in successive sections. A copper junction block 36 threads over the inner end of the shaft and provides a seat for the dielectric pillar 37 of ceramic or sapphire, on the upper end of which is a copper head 38 into which the cap screw 39 is threaded.

The screw body is loose in the plate 29; and its head is spaced above the plate and within the central opening of the annular shorting plate, so that a slight tipping of the plate 29 on the head may occur when the switch is closed to distribute and equalize the pressure between the contacting surfaces and permit accomodation for minor irregularities of the contact surfaces. A coil spring 41 in the head around the cap screw interposes a resilient pressure against the plate to further equalize the pressure of the shorting plate against the contacts 22 and 27.

In order to provide an hermetic seal between the stem and the envelope shell without preventing axial motion of the stem, a generally cylindrical metal bellows 42 is brazed at its lower end to the base of the bearing 33; and at its upper end to the junction block 36.

Cylindrical corona shields 43 and 44 are arranged on the head 38 and junction block 36 respectively to reduce electrostatic stress on the stem; and a third shield 36 extends about the junction block close to the lower closure plate 18 to protect the bellows from tungsten particles generated by the switch contacts. It will be noted that the bellows are isolated physically from the contacts in view of the shielding. Also the contacts are isolated electrically from the bellows in view of the dielectric coupling 37 in the operating shaft.

Referring to the grooves in the ceramic shell, the drawing of necessity exaggerates the relative proportions. Excellent results are obtained if the grooves are .050" to .100 wide with a depth of 7 to /1". Between abutting rings 6 in the upper part of FIG. 1, the groove may be ground or molded all on one ring or half in each abutting face.

With wider shells such as shown in the lower part of FIG. 1, the grooves may be formed in a molding operation or cut preferably by grinding, in either case with as smooth a surface as possible. I know of no way to prevent the vaporization and throwing off of minute particles of tungsten during operation of my switch, and it is an object of this invention to capture these particles and render them harmless to the operation of my switch. These particles sometimes move at high velocity and eventually are deposited on all exposed surfaces on the interior of the shell or envelope.

Where the nature of the surface permits, such a deposit can form a continuous and conductive film leading to flash-over and destruction of the switch. No matter how the vaporized tungsten deposits itself on the exposed inside surface of my grooved shell, the groove surfaces remain relatively free so that continuity of a conductive inner layer of tungsten deposit is broken by the grooves, and there is no tendency to reduce the voltage breakdown of the switch. Because the irregular rough inner surface of the shells tends to catch and retain the migrating tungsten particles, the groove surfaces are made as smooth as possible to deter deposit. Thus as tungsten deposits build up in the zones between the grooves, there is formed electrostatically, an assembly of capacitor elements in series, each element a part of the dielectric envelope body.

FIG. 3 drawn to a larger scale than FIG. 1, better discloses the metallized hermetic joint 51 between successive rings 6 of the shell. In FIG. 4, the interior of the {shell 52 is metallized in narrow bands 53, and thin copper skirts 54 are brazed thereto in overlapping non-contacting relation as shown. In FIG. 5, the shell 56 is grooved, and thin overlapping flanged skirts 57 are mounted in the grooves as shown.

Where the interior walls of a ceramic envelope shell are protected by overlapping skirts as shown in FIGS. 4 and 5, migrating tungsten particles build up a coating on their exposed inner faces, the gaps between the skirts serving to break continuity between them in the same manner as the narrow grooves formed in the surface of the shell.

I claim:

1. An electric switch comprising a ceramic annular body in two parts forming the interior of the switch, a conductive ring interposed between and hermetically uniting adjacent edges of the parts, an annular contact ring concentric with the ceramic body on the inside thereof and conductively supported on the interposed conductive ring adjacent the inner periphery of said ceramic body parts, a conductive plate hermetically closing one end of the ceramic body, a massive contact stud fixed concentrically on the conductive plate within one of said two parts of the ceramic annular body and extending axially into concentric planar alignment with the contact ring and therewith defining an annular passageway communicating the interiors of said two parts of the ceramic annular body when the switch is open, a cap including a bearing hermetically closing the opposite end of the ceramic body, an operator stem slidably arranged in said bearing and including a non-conductive portion adjacent its inner end and having a corona shield mounted thereon to each side of said dielectric portion, a bellows hermetically interposed between the cap and the stem and electrically isolated from the inner end of said stem by said dielectric portion, a circular contact plate substantially coextensive with the contact ring and resiliently mounted on the inner end of the stem adjacent the contact ring and contact stud is movable into and out of engagement with the annular contact ring and contact stud to provide a double-break contact assembly when the switch is open and blocking said annular passageway when the switch is closed, and connector means on the contact ring and contact plate.

2. An electric switch in accordance with claim 1 wherein the ceramic annular body has formed on the inside thereof a plurality of capacitor elements arranged in series formed upon vaporization of the contacts to provide a high voltage breakdown protecting means between said conductive ring forming one terminal and said conductive end plate forming the other terminal of the switch.

3. An electric switch in accordance with claim 2 wherein said capacitor elements arranged in series include spaced apart narrow grooves around the inner surface of the ceramic body.

4. An electric switch in accordance with claim 1 in which metallic skirts of sheet material are separately arranged around the inner surface of the ceramic body in spaced apart relation to divide the inner surface into electrically separated zones and provide a plurality of capacitor elements in series to form a high voltage breakdown protecting means between said conductive ring forming one terminal and said conductive end plate forming the other terminal.

5. An electric switch in accordance with claim 1 wherein at least one of said ceramic annular bodies comprise a plurality of rings having metalized integrally united edges, said rings having grooves extending around the interior thereof.

6. An electric switch in accordance with claim 5 wherein each groove extends around the rings interior surface at its united edge.

7. An electric switch comprising a pair of axially aligned dielectric members, a first fixed contact assembly hermetically interposed between the adjacent ends of the dielectric members and proving an annular contact within the envelope intermediate its ends and terminal lugs outside the envelope, a second fixed contact assembly hermetically closing one end of the envelope and including an end plate sealed across the end of one of said dielectric members remote from the first fixed contact assembly and a stud contact concentrically arranged within the annular contact to provide a pair of radially spaced fixed contact surfaces in planar alignment, an annular shorting plate within the envelope movable to make and break a circuit between the pair of radially spaced fixed contact surfaces, actuator means including a dielectric stern within the envelope supporting the annular shorting plate, a closure plate assembly hermetically sealing the end of the envelope associated with said actuator means and including an expansible bellow movably supporting the dielectric stern, and an auxiliary cylindrical housing surrounding the bellows, and a shield plate mounted on the actuator means within the envelope and interposed between the annular movable shorting plate and the bellows.

References Cited in the file of this patent UNITED STATES PATENTS Re. 21,087 Rankin May 16, 1939 2,976,382 Lee Mar. 21, 1961 FOREIGN PATENTS 563,140 Germany Nov. 3, 1932 569,123 Germany Jan. 30, 1933 389,463 Great Britain Mar. 6, 1933 104,687 Sweden June 9, 1942 571,959 Italy Jan. 17,v 1958 

1. AN ELECTRIC SWITCH COMPRISING A CERAMIC ANNULAR BODY IN TWO PARTS FORMING THE INTERIOR OF THE SWITCH, A CONDUCTIVE RING INTERPOSED BETWEEN AND HERMETICALLY UNITING ADJACENT EDGES OF THE PARTS, AN ANNULAR CONTACT RING CONCENTRIC WITH THE CERAMIC BODY ON THE INSIDE THEREOF AND CONDUCTIVELY SUPPORTED ON THE INTERPOSED CONDUCTIVE RING ADJACENT THE INNER PERIPHERY OF SAID CERAMIC BODY PARTS, A CONDUCTIVE PLATE HERMETICALLY CLOSING ONE END OF THE CERAMIC BODY, A MASSIVE CONTACT STUD FIXED CONCENTRICALLY ON THE CONDUCTIVE PLATE WITHIN ONE OF SAID TWO PARTS OF THE CERAMIC ANNULAR BODY AND EXTENDING AXIALLY INTO CONCENTRIC PLANAR ALIGNMENT WITH THE CONTACT RING AND THEREWITH DEFINING AN ANNULAR PASSAGEWAY COMMUNICATING THE INTERIORS OF SAID TWO PARTS OF THE CERAMIC ANNULAR BODY WHEN THE SWITCH IS OPEN, A CAP INCLUDING A BEARING HERMETICALLY CLOSING THE OPPODITE END OF THE CERAMIC BODY, AN OPERATOR STEM SLIDABLY ARRANGED IN SAID BEARING AND INCLUDING A NON-CONDUCTIVE PORTION ADJACENT ITS INNER END AND HAVING A CORONA SHIELD MOUNTED THEREON TO EACH SIDE OF SAID DIELECTRIC PORTION, A BELLOWS HERMETICALLY INTERPOSED BETWEEN THE CAP AND THE STEM AND ELECTRICALLY ISOLATED FROM THE INNER END OF SAID STEM BY SAID DIELECTRIC PORTION, A CIRCULAR CONTACT PLATE SUBSTANTIALLY COEXTENSIVE WITH THE CONTACCT RING AND RESILIENTLY MOUNTED ON THE INNER END OF THE STEM ADJACENT THE CONTACT RING AND CONTACT STUD IS MOVABLE INTO AND OUT OF ENGAGEMENT WITH THE ANNULAR CONTACT RING AND CONTACT STUD TO PROVIDE A DOUBLE-BREAK CONTACT ASSEMBLY WHEN THE SWITCH IS OPEN AND BLOCKING SAID ANNULAR PASSAGEWAY WHEN THE SWITCH IS CLOSED, AND CONNECTOR MEANS ON THE CONTACT RING AND CONTACT PLATE. 